Field of the Invention
The present invention relates to a technique of failure determination of a detection unit provided in an exhaust system of an engine of a hybrid vehicle.
Description of the Related Art
Among recently developed hybrid vehicles, a vehicle has been developed that allows a travel mode (series mode) in which an engine drives a motor generator to generate electric power and only an electric motor drives travel driving wheels.
Further, for the hybrid vehicle that allows the travel mode, a technique has been developed of performing failure determination of a detection unit (air-fuel ratio sensor, oxygen concentration sensor, catalyst monitor, or the like) in an exhaust system of an engine in the travel mode.
For example, Japanese Patent Laid-Open No. 2011-194976 discloses a technique of stopping fuel supply to an engine and forcedly driving the engine by a motor generator, and performing failure determination of a detection unit in each exhaust system based on a change in a detection value of the detection unit due to the stop of the fuel supply.
There are various failure determination methods of a detection unit in an exhaust system as described above. For example, the methods include a method for determining a failure from a detection value of a detection unit when fuel supply is stopped from a fuel supply state, or a method for determining a failure from a detection value of a detection unit when fuel is supplied from a fuel stop state. Also, a time required for failure determination of a detection unit may differ.
In the hybrid vehicle that allows the travel mode, it is required that various failure determination methods of a detection unit in an exhaust system can be widely performed in the travel mode.